This research project is concerned with the study of mechanisms responsible for changes in growth dynamics in vitro of neoplastic cells treated with glucocorticoids. The emphasis is on those parameters that relate to steroid-induced alterations in the cell periphery. The following aspects are stressed: 1. Qualitative and quantitative fluctuations in nucleotide pools following treatment with glucocorticoids. 2. Involvement of nucleotides in the accumulation of surface glycopeptides and in the alteration of the activity of surface phosphoesterases. 3. Effect of steroids on phosphatidylcholine metabolism of lymphoma line L5178Y.